- If you need clarification, ask it in the comment box above.
- Better answers use proper spelling and grammar.
- Provide details, support with references or personal experience.
Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.
Tip: The max point reward for answering a question is 15.
When the two wires touched the short overheated and blew the output transistor or transistors. The unit needs to be repaired or replaced. It only takes a momentary touch of the wires to blow the output transistor. It is not a fault of your particular amp. It is common to all Solid State amps. Tube amps that have output transformers are not susceptible to this problem. Always shut off the amp when connecting or disconnecting the wires.
Tough one. I repair these for a living. A number of possibilities exist. Likely output transistors are blown on the bad channel. Fuses are likely blown. If the fuses are BLACK inside, don't just put new fuses in, more damage WILL occur. This is a bit more than 'good with a soldering iron' will fix. You need to know how to test an output transistor. You need to look up the transistor type so you know what it is. A service manual will be a big help (I could not find one online.) If more than two outputs are gone on the one side, all should be changed, they are supposed to be MATCHED. Remove and replace all damaged outputs, or replace them all if two are blown. Find the driver transistors and check them for short circuits. After repair, start the amp on a dummy load of a 250watt light bulb to prevent destroying the amp if there is a problem. If you are unsure of any part of this, find an electronics technician to help.
the output transistors are 5 to 10 bucks each for most.there are 2 or 4 on each channel,depending on brand .some high end amps have 10 transistors on each channel.mosfets are a different story as they run 20 to 50 bucks each and there is 2 or 4 on each channel.some amps use a big IC instead of transistors.those have 16 to 24 pins and are easy to change. Those IC are 25 to 75 for a stereo one like stk4141 etc.since most yamaha amps are dc coupled,when the output transistors go,they take out the driver transistors as well.If you replace the outputs and the drive transistors are shorted,they will blow the outputs again.
The unit is only partially smoked. There is a problem in the final output stage, not enough to shut it down completely, but close. The DDT light indicates that the amp is outputing full power. I suspect that there is a partial short that is presenting itself as a low impedence load to the output amp section. This is causing the amp to work really hard and thus the DDT light kicking in. I think you will find 1 transistor shorted or partially so. Replace ALL of the output transistors for that side and that should resolve the problem. Check the driver transistor pair as well. It is important to replace all of the transistors on that side, even if some check OK with a checker.
Thanks for the clarification. From the fuse behavior and feeding the amp into another amp (generally a no-no) it almost certainly is in the output section. If the amp used output transistors (numbered something like Axxxx/Cxxxx where xxxx=0000-9999) there will be some white three-legged low value (.47 ohm or less) resistors that are probably open. FYI the full part numbers for the transistors would be 2SA/2SC so a part marked C3281 would need a 2SC3281. B+D Enterprises (Google them) has most Japanese semiconductors and they have never sold me a fake transistor.
The problem is not the transformer. You now have shorted output transistors at the very least. By corssing the wires you presented a zero(0) ohm impedence load to the output section. It quickly went into overload. Before the fuses had a chance to open up, the outputs fried. This unit will require new output transistors and perhaps the previous driver circuit will require parts as well. Figure on $20-$50 in parts plus hte local labor rate for the repair.
Sounds like the amp has developed a problem. If you had it LOUD then you may have popped a speaker or an output stage. You say it still makes the plugging in noise, what happens when you touch the end of the jack lead whilst plugged into the amp. do you get a burst of clean hum?